1. Field of the Invention
The present invention generally relates to sunscreen compositions that are suitable for topical application to human skin and hair. More particularly, the present invention relates to photostabilized sunscreen compositions having high sun protection factor (SPF) and high UV-A protection.
2. Description of Related Art
The damaging effects of sunlight on human skin have long been noted. In general terms, harmful ultra-violet (UV) rays, particularly those originating from sunlight, which penetrate the upper atmosphere and reach the earth's surface can be classified into two types: (i) high energy UV-B rays (290-320 nm wavelength) which are absorbed just above the dermis and are responsible for sunburn and tanning effects; and (ii) low energy UV-A rays (320-400 nm wavelength) which penetrate deeper into the skin (to the dermis and beyond), and which cause damaging effects that are more long term in nature, such as skin ageing. Continued skin damage resulting from unprotected exposure to ultraviolet radiation can cause more serious conditions such as, for example, skin cancer. Depending on weather conditions, even casual unprotected exposure to the sun's ultraviolet radiation can be detrimental to one's skin. Accordingly, it is generally recommended that a sunscreen product be applied to the skin before exposure to ultraviolet radiation.
Sunscreen compositions or formulations may be applied directly to the skin to combat sunburning of the skin and the numerous damaging effects resulting from exposure to the sun. When a sunscreen formulation, utilizing the proper sun protection factor (SPF, which is a measure of the protection from the sun afforded by a sunscreen agent or composition) is applied uniformly to the body, sunscreens can be highly effective in protecting against sunburn and damage that can lead to photoaging.
However, to the inventors' knowledge, prior formulations were not able to achieve a photostable sunscreen system with a low level of U.S. FDA approved sunscreens while still providing a high SPF and a high UV-A protection level. Therefore, there remains a need to develop novel methods and compositions for high SPF sun protection.